Typical audio sources such as from a CD player, audio amplifier, or mixer generally produce line outputs in the 2Vrms range. Modern integrated circuits built with modern low-voltage processes, however, cannot handle the full range of a 2Vrms signal, so the input signal must be reduced. This is typically done by dividing the input signal prior to the input voltage signal being applied to the integrated circuit for sound processing.
It is beneficial to have a fully differential input to take advantage of the common mode rejection. The negative terminal is a low impedance ground sense path. Using an external resistor divider causes a mismatch between the external ground to each input of the signal processing chip, which will introduce noise.
Embodiments of the invention address these and other limitations of the prior art.